More Hair, Less Reason for It

The labels for Merck's (NYS: MRK) baldness treatment Propecia and enlarged-prostate therapy Proscar, which have the same active ingredient, have been updated to point out links to sexual dysfunction even after the treatments are no longer being used.

Most men are presumably trying to regrow hair, at least in part, to look better for their mate, but the FDA said it collected 421 post-marketing reports of sexual dysfunction from 1998 to 2011, including 59 cases where the sexual dysfunction lasted at least three months after the man discontinued Propecia. There were nearly 200 cases between 1992 and 2010 for men taking Proscar. And there are some reports of male infertility and/or poor semen quality.

While those links haven't caused any notable decrease in sales of erectile-dysfunction drugs, I have to think that most men might find the risk-benefit analysis for the two a little different. Being able to perform in the bedroom ranks pretty high on most men's to-do list.

In theory, the risk is probably pretty low. You can't get a frequency from post-marketing reports, but in clinical trials, sexual dysfunction increased from 2.1% on placebo to 3.8% for those taking Propecia. Of course, some men are going to think any increased sexual dysfunction is too much.

Assuming the new FDA warning only has a modest effect on sales, if any, it won't have a noticeable effect on Merck's revenue. Neither is a blockbuster; Merck sold $447 million worth of Propecia last year and $223 million of Proscar.